Structures at risk with medial double hindfoot fusion: a cadaveric study.

Although discussed as an alternative to triple arthrodesis for hindfoot correction, the published data surrounding the medial double arthrodesis, or fusion of the subtalar and talonavicular joints, has not addressed the proximity of the anatomic structures at risk. A total of 10 cadaver specimens were used to examine the risk of damage to the neurovascular and tendinous structures of the posterior medial hindfoot when performing the medial double arthrodesis. The distance of the reviewed structures was measured in relation to the standardized point of the middle facet of the calcaneus (mean ± standard deviation and range). The proximity of the middle facet to the posterior tibial tendon was 1.88 ± 2.65 (range 0 to 6.65) mm, to the flexor digitorum longus tendon was 5.34 ± 4.79 (range -3.14 to 12.79) mm, to the flexor hallucis longus tendon was 19.08 ± 4.84 (range 13.04 to 27.31) mm, and to the neurovascular bundle was 21.19 ± 7.84 (range 8.36 to 34.26) mm. At the level of the middle facet, the posterior tibial tendon was the largest tendon, measuring 7.14 ± 2.21 (range 3.31 to 10.23) mm by 2.95 ± 0.88 mm (range 1.86 to 4.24 mm; area 22.37 ± 12.23 mm(2), range 6.16 to 43.38 mm) followed by the flexor digitorum longus tendon at 4.25 ± 1.25 (range 1.74 to 5.95) mm by 2.25 ± 0.96 mm (range 1.41 to 4.79 mm; area 8.88 ± 2.62 mm(2), range 6.12 to 14.52 mm) and flexor hallucis longus tendon at 5.75 ± 2.05 (range 2.27 to 8.91) mm by 2.75 ± 0.82 mm (range 1.35 to 4.13 mm; area 16.81 ± 10.05 mm(2), range 4.81 to 36.80 mm). During dissection for the medial double arthrodesis, one can encounter critical anatomic structures, including artery, vein, nerve, and tendon. Our cadaveric investigation found a mean safe distance of more than 2 cm between the middle facet of the talocalcaneal articulation and the inferiorly located neurovascular bundle using the medial double arthrodesis approach.